This invention relates to television synchronizing signal separating circuits.
A composite color television video signal is composed of a video signal and synchronizing signals such as a horizontal synchronizing signal and a vertical synchronizing signal. These synchronizing signals are collectively referred to as the sync signal. A sync separator is employed a clip the sync signals from the composite video signal. These sync signals are then utilized for synchronizing horizontal and vertical scanning with the video signal.
The sync signals are susceptible to various types of noise and distortions. Various schemes have been developed to alleviate these problems. For example, U.S. Pat. No. 4,081,833 described a sync separator which contains circuitry to eliminate hum and peak and pedestal level variations. Another type of distortion that is of concern is time-base distortion caused by hum and tilt on the composite video signal. If the composite video signal is riding on a low frequency hum signal, the leading edge of the sync signal will vary from line to line and the sync separator will be unable to accurately pick off the leading edge of sync.